1. Field of the Invention
This invention generally relates to instrumention for use in the field of measurement of radioactive materials, and more particularly relates to instrumention for the use thereof in the field of Medicine.
2. Prior Art
The use of radioactive gases in making certain medical tests on a patient has been on the increase in nuclear medical laboratories during recent years. When using radioactive gases from a multidose container, the determination of the volume of gas to withdraw for a desired patient dose is complicated by various factors such as half-life of the radioactive material, energy of the material, volume of the container, and attenuation of the gamma rays by the container walls. One method used is to place the source container in the well-type detector of an electronic device called a dose calibrator. If this device has been properly calibrated and adjusted to compensate for the energy of the isotope and attenuation due to the container walls, it will provide a reading of the radioactivity of the material contained therein. Knowing this, and the volume of the container, a calculation of the concentration can be made, and the volume required for the patient dose determined. Drawbacks to this method are (1) the container holding the radioactive gas must be removed from its leaded radiation shield thereby subjecting the operator to a radiation hazard, and (2) this procedure entails several mathematical calculations.
Another method used is to leave the gas container in its leaded radiation shield, remove an aliquot and measure it in the dose calibrator so calculations can be made to determine the amount and concentration of radioactivity in the gas container. Thereafter, the technician can maintain a logbook recording initial amount of radioactivity, time and amount of each withdrawal. If this record is maintained judiciously and a calculation made for radioactive decay just prior to each withdrawal, the following formula may be used to determine the required volume for a standard dose: ##EQU1##
Thus, because of both radiation hazard and complexity of calculations and record keeping, a simple device for storing substantial amounts of a radioactive gas, and rapidly determining the volume required for a standard patient dose, and removal thereof, would be useful in the Nuclear Medicine Departments of all hospitals.